Sulfur Dioxide Mixture Moisture Control for Semiconductor Corrosion
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Solution Overview
Problem
Conventional sulfur dioxide mixtures used in semiconductor microfabrication applications face issues with moisture concentration, leading to metal corrosion and contamination, as the moisture in the gas phase increases during evaporation, causing corrosion and contamination of piping and wafer surfaces.
Innovation Solution
A sulfur dioxide mixture with a controlled moisture concentration range (0.005-5,000 mole ppm in the gas phase and 0.01-50 mole ppm in the liquid phase) is produced by dehydration with a moisture adsorbent and filled into a stainless steel container, maintaining low moisture levels to inhibit metal corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-purity sulfur dioxide with low moisture concentration is filled in a filling container, then the initial moisture concentration is sufficiently low, but the moisture concentrates in the container as sulfur dioxide gas is released, leading to increased moisture concentration in the gas phase
Solution Approach 1:
The patent specifies precise moisture concentration parameters for the sulfur dioxide mixture (5-5000 ppm in gas phase, 0.01-50 ppm in liquid phase) and maintains these parameters throughout storage and usage. By controlling the moisture concentration within these specific ranges and establishing the relationship between gas phase and liquid phase moisture concentrations, the patent resolves the contradiction between achieving low initial moisture concentration and maintaining stable moisture concentration during gas release.
2Productivity
If sulfur dioxide gas is released from the filling container, then the sulfur dioxide gas becomes available for use, but the moisture concentration in the gas phase increases, causing metal corrosion and contamination
Solution Approach 1:
The patent performs preliminary dehydration treatment before filling the sulfur dioxide into the container, reducing the moisture concentration to the specified ranges (5-5000 ppm in gas phase). This preliminary action ensures that even as gas is released and moisture concentrates, the starting concentration is low enough to prevent corrosion throughout the entire usage period.
Solution Approach 2:
The patent establishes specific moisture concentration parameter ranges (5-5000 ppm in gas phase, 0.01-50 ppm in liquid phase) that balance gas availability with corrosion prevention. By controlling moisture concentration within these parameters, the patent enables continuous gas release while maintaining levels below the corrosion threshold.
3Quantity of substance
If conventional dehydration methods are used, then moisture is removed to some extent, but the moisture concentration remains insufficiently low to inhibit metal corrosion during extended storage and usage
Solution Approach 1:
The patent raises the dehydration standard to achieve moisture concentrations of 5-5000 ppm in the gas phase and 0.01-50 ppm in the liquid phase, which are significantly lower than conventional standards. This parameter change ensures reliable corrosion inhibition during extended storage and usage while maintaining sulfur dioxide availability for semiconductor manufacturing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The controlled moisture concentration significantly reduces metal corrosion, allowing the use of stainless steel components without the need for expensive corrosion-resistant alloys, ensuring safe and efficient handling of sulfur dioxide gas in semiconductor processes.
Implementation Method 1
a dehydration step in which a sulfur dioxide mixture having a moisture concentration of 500 mole ppm or more is brought into contact with a moisture adsorbent to make the moisture concentration less than 50 mole ppm
Implementation Method 2
When vaporized sulfur dioxide gas is released from a filling container, liquefied sulfur dioxide evaporates to maintain vapor-liquid equilibrium in the filling container. In that case, since water, which has a vapor-liquid equilibrium constant of about 0.5, evaporates less than sulfur dioxide, water tends to remain in the liquid phase
Data Source
AI summary
Provided is a sulfur dioxide mixture that hardly corrodes metals. A sulfur dioxide mixture contains sulfur dioxide and water. The sulfur dioxide mixture is filled in a filling container in such a manner that a gas phase and a liquid phase exist, and the moisture concentration of the gas phase is from 0.005 mole ppm to less than 5,000 mole ppm.